You need to do changes in your templates\protostar\index.php
file where :
Cut
<jdoc:include type="message" />
<jdoc:include type="component" />
from this code :
<div class="row-fluid">
<?php if ($this->countModules('position-8')) : ?>
<!-- Begin Sidebar -->
<div id="sidebar" class="span3">
<div class="sidebar-nav">
<jdoc:include type="modules" name="position-8" style="xhtml" />
</div>
</div>
<!-- End Sidebar -->
<?php endif; ?>
<main id="content" role="main" class="<?php echo $span; ?>">
<!-- Begin Content -->
<jdoc:include type="modules" name="position-3" style="xhtml" />
<jdoc:include type="message" />
<jdoc:include type="component" />
<jdoc:include type="modules" name="position-2" style="none" />
<!-- End Content -->
</main>
<?php if ($this->countModules('position-7')) : ?>
<div id="aside" class="span3">
<!-- Begin Right Sidebar -->
<jdoc:include type="modules" name="position-7" style="well" />
<!-- End Right Sidebar -->
</div>
<?php endif; ?>
</div>
and paste it after position-7 or before postion-3, whichever side you need to show your content, i.e.
<div class="row-fluid">
<?php if ($this->countModules('position-8')) : ?>
<!-- Begin Sidebar -->
<div id="sidebar" class="span3">
<div class="sidebar-nav">
<jdoc:include type="modules" name="position-8" style="xhtml" />
</div>
</div>
<!-- End Sidebar -->
<?php endif; ?>
<main id="content" role="main" class="<?php echo $span; ?>">
<!-- Begin Content -->
<jdoc:include type="modules" name="position-3" style="xhtml" />
<jdoc:include type="modules" name="position-2" style="none" />
<!-- End Content -->
</main>
<?php if ($this->countModules('position-7')) : ?>
<div id="aside" class="span3">
<!-- Begin Right Sidebar -->
<jdoc:include type="message" />
<jdoc:include type="component" />
<jdoc:include type="modules" name="position-7" style="well" />
<!-- End Right Sidebar -->
</div>
<?php endif; ?>
</div>